I have been collecting germanium transistors and diodes for over thirty years, and pre-Intel integrated circuits for ten. Over that period I have come across a number of types that remain a mystery to me. A few are complete unknowns, but for most of them I know, or can guess, the manufacturer, but have no characteristic data in my extensive library of databooks, datasheets, advertisements, magazines etc. This page shows some of the most interesting examples.

I am seeking any kind of information on all of these, apart from the manufacturer name. If you have any, please


AUDIO transistor This weird thing was described by the chap who sent it as an 'AUDIO' transistor made by Philco in the USA. I have subsequently found a second one. It appears to be a metal shell in two parts, joined at the flange around the middle, possibly containing a smaller device. It looks a bit like a nuvistor, but has only three leads. I have no other information about it so if you know anything at all, please


CXT6b transistor This Mullard power type uses their early package mainly found on the OC16. The CXT prefix is possibly a UK GPO (General Post Office) designation, but I'm not sure. I have one other type, the CXT1. If you anything about the series, please


EW81 transistor This delightful medium-power type uses the early GEC packaging and has an 'experimental Wembley' number. This series was used for prototypes that were released in small numbers before being given a GET number if successful, consequently characteristic data are hard to come by. If you have any information on the EW series, please


GET118 transistor Here's another GEC device, the GET118, although mine is marked MULLARD because it dates from after the so-called joint-venture in which Mullard took over GEC's transistor production. I have extensive data on the GET series, however this one number is omitted. Why? It is also most unusual in having a white sleeve. If you know anything about it, please


CS2-C diode? This is a BTH branded device, in the 'form C' ceramic tube with metal end caps that they used for diodes. However, I can find no information about a CS series. If you know anything about it, please


GT50 transistor This BTH/AEI type GT50, and its modified form GT50B, are in a similar situation to the GET118 above: I have extensive data on the GT series, however this one number is not included. Why? If you know anything about it, please


GET587 transistor This TO-3 power type seems to have been made by Mullard but is numbered GET587 which should mean that GEC made it prior to the 'joint venture' with Mullard. I have extensive data on that series, however this one is not included. Why? If you know anything about it, please


MEI transistor Another oddity: a Mullard type in their standard SO-2 glass capsule, apparently marked MEI or possibly ME1. I have some examples with coloured rubber bands around them. I know nothing about this type, if you do, please


NC11 transistor The source of the MEI above also provided some of these Mullard NC11 in the standard SO-2 metal capsule. I have subsequently found an STC transistor with the same part number, as shown. I know nothing about this type either, if you do, please


XD201 diode A sub-miniature diode this time, in the BTH 'Form H' glass body with plastic sleeve. No branding though, just the part number. I'm unaware of an XD series by BTH, but does XD stand for 'experimental diode'? If you know anything about it, please


RS-10 transistor This device looks like a transistor, with three leads. It is printed RAYS RS-10. I'm fairly sure that RAYS is not Raytheon. If you know anything about it, please


OA203 diode Rather surprisingly, this Mullard diode OA203 is not included in the numerous Mullard data books and sheets that I possess. If you know anything about it, please


HS1.5/1 diode Here is a Fujitsu diode type HS1.5/1, or is it a fuse? I have almost no data for early Japanese diodes. If you know anything about it, please


AF6 transistor This is a transistor type AF6, with a logo consisting of the letters ECM in a diamond frame. Radiomuseum has other similar AF types, but like me, do not know the manufacturer or device data. If you know anything about it, please






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